1. Field of the Invention
The field of the invention is that of tapping attachments for providing tapping in a radial direction, that is in a direction different from that of a driver member from a driving machine. In particular, the invention relates to radial tapping attachments which are self-reversing.
2. Description of the Prior Art
The field of the invention and prior art patents are exemplified in the field of self-reversing tapping attachments by reference to prior patents of the inventor of the invention of the instant application. These include U.S. Pat. Nos. 3,999,642, 4,014,421, 4,705,437, and 5,209,616, and patents cited therein, all of which are hereby incorporated by reference herein.
The aforesaid patents disclose and claim self-reversing tapping attachments including a tap-holding spindle together with simultaneously rotating forward and reverse drivers, the spindle being freely floating and moveable axially with respect to the forward and reverse drivers. Under the influence of the forward driver, the tap in effect screws itself into the hole being tapped in the workpiece. Upon cessation of feed by the tapping machine and retraction of the tapping machine, causing relative axial movement between the tap holding spindle and the driver members, the forward drive member becomes disengaged from the tap spindle. Upon further retractive movement by the tapping machine, additional relative movement occurs whereby the reverse drive member becomes engaged with the tapping spindle, causing reverse rotation of the tap spindle and unscrewing the tap from the hole. In this manner, self-reversing is accomplished.
With high-speed, computer numeric controlled (CNC) machining centers, the capability afforded by said U.S. Pat. No. 4,705,437 is particularly pertinent. Under the '437 patent, the gear arrangement is such that in particular embodiments forward and reverse drive members rotate at different rates of speed, to achieve the desirable result of reducing excessive wear.
Recently, further progress has been made in tapping through improvements in CNC lathes. As a consequence of this, utilization has increased of radial tapping. This is tapping which is accomplished by a tap cutting in a direction transverse to the direction of the driving part from the driving machine. Such radial tapping is utilized, for example, where space is at a premium, where the configuration of the workpiece and the working space are such that axial tapping is inconvenient or unfeasible, or where the workpiece is such that it is more effective to tap it radially than axially.
Existing radial tapping attachments require the driving machine to reverse itself in order to remove the tap from the workpiece upon completion of tapping. This has drawbacks in particular with respect to computer numeric control devices, creating delays and complications tending to diminish some of the advantages of tapping from automated driving machines. Such machines are most advantageously programmed to feed the driving part to the tapping attachment and then to withdraw, as opposed to reversing rotation.
Therefore, there has been a felt but unfulfilled need for a self-reversing tapping attachment for use in connection with radial tapping.